For questions concerning the "power-menu" (which pops up when long-pressing the power button)
What are "power-options"?
On many devices, when your display is switched on and you long-press the Power button, a menu appears. From this, you can at least chose to power-off the device. Most times this menu also holds options to reboot, take a screenshot, or switch to airplane mode. On some custom ROMs, you might see additional options like e.g. booting to recovery.
different power menus